During the production life cycle of oil and gas extraction from reservoir fields in geological formations, certain stages are followed which include exploration, appraisal, reservoir development, production decline, and abandonment of the reservoir. Important decisions must be made at each of these stages in order to properly allocate resources and to assure that the reservoir meets its production potential. The planning and the decisions are typically part of a process referred to as a Field Development Plan (FDP).
In the early stages of the production life cycle, one begins with almost complete ignorance about the distribution of internal properties within the reservoir. As development continues, diverse types of reservoir data are collected, such as seismic, well logs, and production data. These reservoir data are combined to construct an evolving understanding of the distribution of reservoir properties in an earth formation. This understanding is key to making proper reservoir management decisions.
As oil and/or gas is extracted from the reservoir, new data are obtained and the goals and development plans for managing the reservoir are periodically re-evaluated to maximize production of oil and/or gas from the reservoir. As the reservoir is depleted, the goals and field development plans are changed, and eventually the reservoir is abandoned.
Various prior art approaches the oil and gas industry has taken to reservoir management have been reported in numerous books and technical journal articles. Methods which describe the use of a reservoir model in combination with experimental design techniques to determine the sensitivity of production plans to the uncertainty associated with technical parameters are described, for example, in published U.S. Patent Application No. 2005/0096893 to M. Feraille et al. and U.S. Pat. No. 7,054,752 to 1. Zabalza-Mezghani et al.
Co-owned U.S. Pat. No. 6,549,854 to A. Malinverno and M. Prange describes model-consistent update strategies for subterranean reservoirs taking into account uncertainties of measurements. Co-owned U.S. Pat. No. 6,980,940 to O. Gurpinar et al. and published U.S. Patent Application No. 2003/0225606 to B. Raghuraman and B. Couet together with the literature cited therein describe many detailed steps relevant to current reservoir optimization methods.
More recently published U.S. Patent Application No. 2007/0192072 to A. S. Cullick et al describes methods to optimize field production using reservoir simulators and proxy models to determine sensitivities of control parameters and future settings of control parameters.
The prior art described above relates mostly to production optimization and the placement and use of fixed installations or assets. However, in the course of assessing and producing hydrocarbon bearing formation and reservoirs, it is important to acquire knowledge of formation and formation fluid properties which influence the productivity and yield from the drilled formation. Typically such knowledge is acquired by mobile tools and methods generally referred to as “logging”.
Logging operations generally include the measurement of a formation parameter or formation fluid parameter as a function of location, or more specifically depth in a wellbore. Formation logging has evolved to include many different types of measurements including measurements based on acoustic, electromagnetic or resistivity, and nuclear interactions, such as nuclear magnetic resonance (NMR) or neutron capture, or mechanical forces as generated by the flow through the well and the production tubing.
Another form of logging tool is known as a formation sampling device and is designed to take samples of formation fluid at one or more depth points. A representative example of such a sampling device is the MDT™ tool of Schlumberger.
It is further well established to mount logging tools on either dedicated conveyance means such as wireline cables or coiled tubing (CT) or, alternatively, on a drill string which carries a drill bit at its lower end. The latter case is known in the industry as measurement-while-drilling (MWD) or logging-while-drilling (LWD). In MWD and LWD operations, the parameter of interest is measured by instruments typically mounted close behind the bit or the bottom-hole assembly (BHA). Both logging in general and LWD are methods known as such for several decades and hence are believed to require no further introduction.
In addition to the logging measurements described above, it is possible to test the performance of a well using flow measurements conducted at the surface.
At present, any of the above logging and well test measurements are chosen by an operator based on experience and are only loosely correlated to a field development plan or an objective function based on the field development plan
In view of the known art, it is therefore seen as one object of the invention to improve and enhance methods for selecting logging and well testing tools and methods in an automated or semi-automated manner.